Description
We produce a supercontinuum light source that is generated from a femtosecond oscillator and coupled into a micro-structured fiber. The broad band light source is used in combination with a programmable spatial light modulator to produce both integer and fractional value optical vortices. We then show that this system allows for independent control over the vortex size, shape, position, charge, and wavelength. Multiple vortices are generated by segmenting the spatial light modulator, and filters are used over each segment to produce vortices of different wavelengths. We examine the interference between multiple vortices for equal and opposite charge as either coplanar or with a phase tilt resembling spatially separated phase patterns on the spatial light modulator. Fractional vortices are analyzed in the zeroth order and diffracted into the first order from a blazed grating. In particular, improperly calibrated fractional vortices diffracted into the first order are studied and compared to the result from proper calibration. The outcome for improper calibration is a vortex in the first order that leaves the fractional diffraction from the phase discontinuity in the zeroth order. The generation and interaction for integer and fractional valued vortices are analytically and numerically predicted, and the experimental results for up to four high quality optical vortices with multiple wavelengths are generated from a single light source and spatial light modulator. We examine the experimental results and see that they show exceptional agreement with the analytic and numerical predictions.
